Wildlife Exploitation

setting limits for wildlife harvest

• what do you need to know

  • how fast they reproduce

  • when they reach sexual maturity

  • carrying capacity

  • population demographics

    • N_e

  • MSY

  • OSY

    • preferable to use 

MYS vs OSY

• Maximum sustainable yield goals have largely been replaced by Optimum Yield goals

• Avoids over-harvesting when MSY assumptions are not met 

• Definition of Optimum Yield:

  • Will provide greatest benefit to the nation, with reference to food production and recreational opportunities

  • Prescribed as such on a maximum sustainable yield as modified by any relevant economic, social or ecological factors

regulating harvest in the US

• Data input

• Harvest based on current conditions

  • Population size

  • Habitat

  • Reliability of data

• Predict the size of the population and possible harvest rate for that year

  • Precautionary principal utilized—be conservative in setting limits

    • Data less certain or absent

• Update annually

  • Data

  • Public input

  • Agency decision

• This represents Adaptive Harvest Management strategy

• decision making for wildlife harvest rates

  • main goals

• Provide recreational use of wild game

• Have that use be sustainable

• Have that use be consistent over time

• More recent times:  Make the decision-making process transparent and replicable

  • What science was consulted?

  • What values were identified?

    • hunters

    • farmers

    • aesthetic 

• decision making for wildlife harvest rates

  • art or science

• Aldo Leopold (1933) wrote: “game management is the art of making land produce sustained annual crops of wild game for recreational use”

• Actually, it is the integration of wildlife science with values-based judgement

• harvest considerations

  • Demographic effects

• Impacts on age structure and sex ratios

• harvest considerations

  • Genetic effects

• Highly valued attributes that may be genetically controlled may be impacted (e.g. antler size, horn size, lion mane, etc.)

• Focusing on one sex may impact effective population size (e.g. hunting males in a monogamous social system may reduce genetic diversity in the population)

PrOACT

• problem objective alternatives consequences tradeoffs

• structures design making framework

• need to gather data on problem 

• come up with objectives

• come up with alternatives

  • like car shopping

• think of consequences

• tradeoffs and optimization

• decide and take action

• look at the results

  • rinse and repeat

Hierarchy of generic fundamental objectives for wildlife management

1. Maximize ecological benefits

• a. Maximize persistence of native species (or communities)

• i. Maximize population size

• ii. Maximize distribution

• iii. Maximize individual quality

• iv. Maintain genetic and species diversity

• b. Minimize nonnative and invasive species (or communities)

• c. Maintain ecosystem function

• Hierarchy of generic fundamental objectives for wildlife management

  • 2. Minimize costs

• a. Minimize capital (fixed) costs

• b. Minimize ongoing (variable) costs

• Hierarchy of generic fundamental objectives for wildlife management

  • 3. Maximize public and private benefits (utilitarian benefits)

• a. Maximize consumptive recreational benefit

• b. Maximize non-consumptive recreational benefit

• c. Maximize public services (e.g., energy generation,

• water delivery)

• d. Maximize public health and safety

• e. Maximize private economic opportunity

  • hotel, bar, restaurant 

• f. Provide sustainable subsistence use, where appropriate

• Hierarchy of generic fundamental objectives for wildlife management

  • 4. Facilitate cultural values and traditions (non-utilitarian benefits)

• a. Maximize aesthetic and spiritual values

• b. Minimize taking of life

• c. Treat animals in a humane manner

case study of wolf hunting in montana

• fundamental objectives

  • Need to define wolf management units for hunting opportunities and to reduce conflicts 

  • Livestock interests

  • Ungulate hunters

  • Anti-wolf hunting interests

• Process objectives:

  • 7. Enhance open and effective communication to better inform decisions

  • 8. Learn and improve as we go

• Strategic objectives:

  • 9. Increase broad public acceptance of harvest and hunter opportunity as part of wolf conservation

  • 10. Gain and maintain authority for the state of Montana to manage wolves

adaptive harvest management

• waterfowl

  • Objectives:

    • Maximize annual harvest

    • Maintain sustainable level of harvest

    • Maintain population size close to or higher than management plan goals

    • Prevent closed seasons, except in extreme circumstances

  • Predictive models used to quantify:

    • Expected harvest 

    • Breeding population in subsequent year

Uncertainty in models:

• Density dependency of recruitment?

  • predation

• Harvest mortality compensatory or additive?

• Uncertainty matters…models lead to very different harvest strategies

Importance of wildlife to people

• Nutritional value

• Economic value (both income & pest control)

• Cultural value

Impact of harvest

• Lowers population densities

• Reduce average body size

• Lower average age at reproduction/reduce # of older individuals in population

• Decrease fecundity

  • because they are so much younger

• Local extirpation of vulnerable species

  • small niches of species

• Change size and structure of community

  • Decrease representation of large-bodied species

  • Change composition—change representation in different trophic guilds

  • Decrease in production overall

sustainable harvest attributes

• No consistent decline in numbers

• Density not reduced where vulnerable to local extinction

• Ecological role of species not impaired

• Not reduced to density that doesn’t support human needs

factors affecting sustainability

• Proximity to “Source” area—closer to protected area, the more sustainable

  • where do you have the most animals

• Easy outsider access decreases sustainability

  • you might have outside people coming into your managed area

• Proximity to market or commercial centers decreases sustainability

  • easy access to a market

additional biological factors

• Low forest productivity tends to be less sustainable

• Wildlife population densities highly variable

• If population is lowered below maximum productive (1/2K)

  • In tropical forests, pop. often at 30% of carrying capacity or lower due to over-exploitation

human factors affecting sustainability

• Human Population Density

  • Increased growth of human population

  • Decreased forest area increases impact

  • Increased immigration into area

  • Sedentary populations increase impact

    • more likely to overutilize resources 

• Hunting Technology

• Hunting Proficiency

• Use of domestic animals can reduce impact of human population

conditions that detract from sustainability

• Logging operations

• Road construction

• Government sponsored translocations of people

• “Pacification” and sedentarization of indigenous people

• Commercial trade in wild meat (“bushmeat”) &/or skins

identifying management goals

• species conservation

• no consistent decline

• not vulnerable to extinction

• maintain ecological role

• identifying management goals

  • ecosystem conservation

• species richness and diversity

• primary productivity maintained

  • concerns logging

• nutrient cycle maintained

• identifying management goals

  • human livelihoods 

• catch or harvest maintained

• wood and non timber yields maintained

tragedy of the commons

• Common resource, with open access and no regulation, can be over exploited

• If managed for the common good, could benefit all, but “cheaters” can benefit more to the detriment of the resource and the common good

• Prior to regulations, wildlife resources suffered from this situation in US

• Whales endangered due to unregulated hunting—Whaling Commission and US Marine Mammal Protection Act placed the harvest under regulation

• Tropical forests and wildlife currently threatened—”bushmeat”

• Oceanic, marine fisheries still suffer from this social dilemma

over exploitation and life history

• Some species can compensate for exploitation (i.e. coyote), but most can’t

• Species with “slow” life histories (usually long-lived, with low reproductive capacity) more vulnerable to over exploitation

• High extinction risk associated with:

• Small geographic range

• High trophic level

• Low population density

• Long gestation

• High body mass